Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a second image in a sequence thereof;

FIG. 3 is the third image in a sequence thereof; and,

FIG. 4 is the fourth image in a sequence thereof.

The outermost broken line illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines depict portions of the graphical user interface that form no part of the claimed design.

The appearance of the graphical user interface sequentially transitions between the images shown in FIGS. 1-4. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 